Semiconductor light emitting devices (LEDs) are typically covered with an optical element to protect the semiconductor structures, increase light extraction efficiency, and assist in focusing the emitted light. One type of material used to encapsulate LEDs is epoxy. Epoxy, however, is a low refractive index material and thus is not as effective as a higher index material at reducing losses due to total internal reflection at the semiconductor/low index encapsulant interface. Further, epoxy and other organic encapsulants typically suffer from yellowing when used with LEDs that operate with high temperature and/or short wavelengths. Moreover, epoxy encapsulants typically have coefficients of thermal expansion that poorly match those of the semiconductor materials in the LED. Consequently, the epoxy encapsulant subjects the LED to mechanical stress upon heating or cooling and may damage the LED.
Thus, an improved optical element with increased light extraction efficiency and is resistant to yellowing or other degradation and a method of bonding such an optical element to an LED is desirable.